Chapter 11 Lecture Notes
Chapter 11 Lecture Notes BISC 2202
Popular in Cell Biology
Popular in Biological Sciences
This 3 page Class Notes was uploaded by Lareb Notetaker on Tuesday October 27, 2015. The Class Notes belongs to BISC 2202 at George Washington University taught by Oren, M in Fall 2015. Since its upload, it has received 74 views. For similar materials see Cell Biology in Biological Sciences at George Washington University.
Reviews for Chapter 11 Lecture Notes
Great notes!!! Thanks so much for doing this...
-Dr. Terrence Kirlin
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 10/27/15
Lareb Altaf October 26 2015 Chapter 11 Membrane Structure Membrane o Membranes are one of the most important parts of the cells Living things need to keep internal environments different from their external environment o Serve as a selective a barrier plasma membrane found in all cells o In Eukaryotic cells there are internal membranes for organelles that keep even more of a speci ed environment along with plasma membrane o In unicellular organisms ex bacteria there is a similar communication system Cell needs to know where is the food areas to avoid Membrane Functions o Receiving informations import and export of small molecules capacity for movement and expansion In multicellular organisms they have multi communications between all organelles Import and Export actively and non actively of molecules Also membrane allows movement and growth expansion of the cell Membrane Structure o Membraneenclosed organelles in eukaryotic animal cells ER nucleus peroxisome lysosome golgi apparatus plasma membrane mitochondrion transport vesicle 7 w Membranes are made of lipid bilayers Very thin 5 nm in M 2 thickness When compared to bacteria bacteria is 3 microbes ifquot 39 39 39 almost a thousand times smaller The lipid bilayer is made of W WWW many proteins and phospholipids Contain more lipids than mm W W protein molecules Have glycol a to proteins glycol lipids oA typical membrane lipid hydrophilic head hydrophobic tails Phospholipids hydrophilic head polar groupphosphateglycerol two 9 hydrophobic fatty acid tails oPhosphatidylcholine is the most common phospholipid in cell membranes oDifferent types of amphipathic membrane lipids Phospholipid has a serine residual Cholesterol based on a steroid molecule Glycolipid which contains a covalent link sugar such as galactose o Hydrophilic Molecule polar molecules which bonds with water molecules Sometimes they are hydrogen bonds and electrostatic bonds yellow lines in this case acetone which is soluble in water o Hydrophobic molecules cluster together because water molecules hover around it When you have more than one molecule they will cluster together because they are repelled from the water surrounding it and the hydrogen bond makes it come together Ex When oil is placed in water it becomes clustered together oBilayer structure is energetically favorable for amphipathic molecules if W 1 mm mm you put phospholipids in water they will m from the following shape lipid bilayer l The problem here is that the bilayers on protein molecules lipid 39 agitggwszgzrszam the hydrophobic sides are still exposed so a 1m a sphere would be more ef cient natural state of bilayer Sealed structure is energetically favorable for amphipathic molecules o Arti cial lipid bilayer aka liposomes created arti cially in order to study the membrane and the components of the membrane You can play with the different percentage of different types of lipids You can study membrane proteins and how they affect in uence the shapes lateraldi usion and sizes of the liposomes Minimum size is 25 nm but can get up to 1 mm lt gt o Membranes behave as twodimensional uid can have lateral diffusion ip op rarely occurs exion and rotation ipmp o Membrane uidity is effected by the length and the level of saturation of the rarely occurs lipids carbon tails two main factors are More double bonds more uidity T y The longer the tails the increased uidity it contains new mm Lareb Altaf October 26 2015 Cholesterol Structure 3 o Have a polar head followed by a rigid planar steroid ring structure and a non polar lag hydrocarbon tail The direction in which they are squeezed with in the phospholipid 2 membrane allows them to become more rigid o Cholesterol constitute 20 percent of animal cell membrane It makes it more rigid o Membrane assembly start at the ER The nuceaus is surrounded by the double bilayer membrane which is an extension of the ER where proteins are made The Golgi Apparatus is where protein modi cation such as glucoseligation and phosphorylation takes place The mitochondria contain a double bilayer protein Membraieeaglslemblyat oMembrane assembly at the ER approximately symmetrical Same on both quotquotquotquot sides of bilayer The new membrane is derived by phospholipid synthesis Newmembma which adds to cytosolic half of the bilayer Enzyme interchanges lipids to other Smblase sides called Scramblase which catalyzes transfer of random phopholipds from sf one monolayer to another This produces the ER Censmaimsmy WM membrane which is symmetrical on both sides like heGdg appmm M the Original39 From the ER gt oCells maintain an asymmetry at the Golgi apparatus W This is the symmetrical membrane that comes from the ER The Flippase is an enzyme which catalyzes transfer of speci c proteins phospholipids to a Flippase speci c side of membrane cytosolic monolayer This process produces the Golgi membrane o The cell is maintaining distinct inside and outside faces of the membrane extra and intracellular side The internal cellular is sometimes residual to the extracellular of the membrane Structure of nal cellular membrane with all kinds of sugar stored on the outside sphingomyelin glycolipids phophatidycholine phophatydilinositol phosphatydilserine phophatydiletanolamine o Membrane proteins compose of more than 50 of material in the protein hydrophobicamimdd Functions transporters and channels anchors receptors and enzymes Side aiquot Protein associations with the cell membrane in all kinds of different ways such as the transmembranal monolayerassociated alpha helix only on one layer of the bilayer perpendicular lipidlinked outside of the membrane proteinattached protein attached to another protein peripheral membranal proteins The backbone of a polypeptide chain is hydrophilic because it s polar The best way to create a hydrophobic environment is to cancel all charges on the backbone by creating a alpha helix backbone cancels charges via hydrogen bonds Many of the transmembrane peptides are a alpha helix Many of the singlepass transmembrane proteins are receptors for extracellular signals pore transcmgrane oMulti alpha helical membrane protein Ion channels multipass protein Each of the aqueous pores are alpha helix polar hydrophilic allows water soluble molecules to go through image to the left oPorin Protein beta barrel structure best way to mgmii 39 39 7 cancel polarity of back bone but less common Pidbi39a e39 quotquot db h e39 The can create mores in mitochondria o We know complete protein structure of only a few membranes 3D Structure o Xray crystallography based on pure high quality protein able to extract and isolate m m x to create crystals Dif cult to make unless you have very good protein WIIW i eeeeeee m hydrogen bond o Detergents are lipidlike protein molecules have hydrophilic head hydrophobic quotmazesquot tails used to break down disul de bonds of proteins sometimes o Emulsi cation disruption of the lipid bilayer detergent micelles and watersoluble A mt mixed lopeddetergent micelles used to separate detergent proteins quot w tt imilquot Lareb Altaf October 26 2015 o The protein structure of bacteriorhodopsin by Xray crystallography used to trap photos of the light to create energy to transfer against the gradients of hydrogen ions toward the outside in order to use in an electron transport chain to create ATP energy Cell Membrane Structure Support o Picture depicts red blood cells o Cell Wall in plants fungi and bacteria Cell cortex in eukaryotes o Cell Cortex in red blood cells blood cells don t need to do much interaction With other cells Mousehuman hybrid cell oMovementof proteins across the membrane uid mouseceu EX of eXperlment done to create hybrid human and melamine 39 mouse cells 4 5 lgj membrane protein uorescein labeled membrane 7 labeled protein C D human cell protein A o Membrane domains a molecules in cytosol c sometime in A ti ht polarity of cells can be due to interaction of other cells d barriers of apicmm l l jugncuon other cells that can bind proteins in speci c place 3 We o Epithelial cells of the gut are polarized by tight junctions One side 165 stores gut While the other side stores basal plasma With complete memb39a different function pictured to the right o Carbohydrates on the cell surface cell closing several types they t rrrrr are glycolipids glycoproteins Which contain short carbohydridt tails 39 39 and longer sugar chains Function of the sugars creates slimy due to interaction With water and sugar adhesion protein protection amp communication oCarbohydrates play a roles in cell protection cellcell adhesion preventing adhesion of cells to surfaces lubrication permeability Cell tissue adhesionpictured below basal lamina CVTOSOL O O O O O O neutrophil BLOOD LECTINS RECOGNIZE O O g ggggg ATES 0N NEUTROPHIL ROLLS blood 0 o ALONG BLOOD ADDITIONAL INTERACTIONS Vesse39 s f o VESSEL WALL ALLOW NEUTROPHIL TO peCI IC 0 O oligosaccharide i MIGRATE INTO INFECTED TISSUE Iectin W W 390 O TISSUE endothellal cell 0B